Death Toll Now 13 in Deadly California Mudslides

But it was the fire that led to the mudslide, by burning away vegetation.

This is why mudslides are so risky - they build speed so quickly and get bigger as they pick up extra debris so can't always be predicted by rainfall.

He added several dozen homes were destroyed or severely damaged, and that there are probably many more in similar condition in areas still inaccessible.

Local fire chief Anthony Buzzerio said around three quarters of the affected area has now been searched - with some rescuers falling down manholes and into swimming pools that have been covered up.

On Instagram, Ms Winfrey said her property had escaped the worst as she toured the scene, but described the house next door as "devastated".

More than 50 people have been rescued from rooftops after trees and power lines blocked roads.

Anderson says the number dropped because people were located, but it could continue to fluctuate greatly.

"Right now our assets are focused on determining if anyone is still alive in any of those structures that have been damaged", Santa Barbara County Sheriff Bill Brown said. "Many chose to stay in place", Brown said.

Heavy rains sent rivers of mud tumbling down hillsides Tuesday, demolishing homes in the affluent seaside community of Montecito weeks after a massive fire charred the area last month.

U.S. Highway 101, a crucial link between Ventura and Santa Barbara, was so overwhelmed by mud and debris that authorities announced it will remain closed until at least Monday.

Berkeley Johnson said he and wife Karen climbed through a window to their roof around 3 a.m. after mud and rocks came crashing into their home and dumped eight feet of mud on their staircase.